Hi Eric,
Are the links to your own website within the blog post followed?
Is your guest blog post indexed by Google?
Is the Blog that you posted your article on ranking for it's own brand terms (i.e. not penalised)?
If you can answer yes to these three questions then there is a very high chance that PageRank (or link juice if you prefer) will be passed from the guest post to your site, how much that moves the needle is subjective.
As Tom advises it is much better to try to aim your guest post efforts at sites that has an audience:
When I am qualifying sites for guest post opportunities then I will check the following:
1. Their articles receive a large number of social shares
2. They have a large RSS subscriber base or email list
3. The blog posts receive comments
There is a good post by James Agate on this topic over on the Moz blog
Ideally you want to be posting on places that your customers will hang out however they maybe direct competitors and it will be impossible to secure an opportunity.
For my clients I make sure the blog’s topic is relevant to the company’s (brand) readership/customers. I make sure the blog content is in line with the buyer personas outlined and their marketing journey, this does not necessarily mean that they are within the same niche but could be in a complimentary niche.
These guest posting opportunities will probably be a little tougher to secure but the extra effort will be worth it in terms of links, social shares and referral traffic.